Base of Operations: Unrevealed
formerly the Mountain Temple of Zokk, in the dimension of Katharta
formerly an unnamed world which may or may not be associated with the realm of Katharta

First Appearance: Giant-Size Man-Thing#3 (February, 1975)

Powers/Abilities: Mortak is an accomplished warrior, skilled in hand-to-hand combat as well as in the use of bladed weapons. I'm betting he doesn't bathe very often, however. He commands an army of barbarian warriors, of unidentified size.

(Giant-Size Man-Thing#3 (fb) - BTS) - Mortak comes from a world separate from the landmass of Katharta, and it uncertain if he is from another dimension altogether. He rules a kingdom on that world, and seeks to rule all ten kingdoms of his own world. He became allied with the wizard Klonus and his lackey Tai under unknown circumstances.

(Giant-Size Man-Thing#3 (fb)) - Mortak's armies, assisted by the magics of Klonus, attacked and conquered of the city of Katharta. Its army was slaughtered, its crops were burnt, and its women were put into service of Mortak's soldiers. The king of Katharta was slain, and its prince, Korrek, was captured and held in chains in their prison for one year.

(Giant-Size Man-Thing#3) - While Mortak was happy with ruling Katharta and taking over the ten kingdoms of their own world, Klonus wanted more. There was/is a legend of some unknown cosmic significance behind Korrek that he or whoever rules Katharta is destined for godhood. Klonus waited until for the proper time (some sort of astral alignment sort of deal, most likely) to slay Korrek to gain the full power. Klonus then had Korrek staked out on top of the Mountain Temple of Zokk, and summoned the Serpent Hawks to sacrifice the barbarian prince.

However, Korrek's ally, Dakimh the Enchanter sent the Man-Thing to Korrek's aid. The Man-Thing slew Klonus's warrior servant, Tai, and freed Korrek. Klonus fled with Mortak to avoid the Serpent Hawks who would now be hungry for a different meal. Jennifer Kale teleported the Man-Thing and Korrek to Dakimh's castle to discuss the significance of the recent series of events.

Klonus traveled to Citrusville, Florida, where he drew power from the Nexus of Reality in "The Man-Thing's swamp" and prepared to make his stand against Dakimh and his allies. While Klonus occupied Dakimh and the Man-Thing, Mortak engaged Korrek himself. Mortak's sword shattered against Korrek's enchanted blade, and Korrek overpowered Mortak in hand-to-hand combat. The Man-Thing, who had destroyed its opponent, smashed Klonus in the head from behind, incapacitating him. Jennifer formed energy cocoons about Klonus and Mortak and banished them into space.

(Man-Thing I#21 / Man-Thing I#22) - The demon Thog freed Klonus and Mortak and returned them to Earth to oppose the Man-Thing. Klonus succeeded in weakening the Man-Thing by tapping into his diluted, dispersed brain and bringing out portions of Sallis' mind, which confused the bog-beast. Mortak further confused it by skewering it with a pole, sending Sallis' mind further into a state of shock.

With the Man-Thing incapacitated, Thog arrived and attempted to use his plot involving the Nightmare Boxes to drive the cosmos into insanity. However, the efforts of the Man-Thing, Dakimh's spirit, and even Steve Gerber himself, caused the Boxes to implode, pulling Klonus, Mortak, Thog, and the demons of Sominus into it. Within the box, the Man-Thing destroyed Thog, effectively ending the threat of the Nightmare Boxes. Gerber, Dakimh, and the Man-Thing escaped back to Earth, but Klonus and Mortak's fates were not seen.

Katharta is listed as a dimension, yet Korrek sees a village aflame and states that all of Katharta was in flames. Perhaps Katharta is one city within a larger realm, and/or Katharta is the name of the capital city and the dimension, much like Asgard.

It is unclear whether the "one year" of waiting is a topical reference. It seems like a long time to wait, but it is also quite likely that time passes quite differently in the various dimensions involved.